You mentioned the Navy, for example, and that we have fewer ships than we did in 1916. Well, Governor, we also have fewer horses and bayonets, because the nature of our military's changed. We have these things called aircraft carriers, where planes land on them. We have these ships that go underwater, nuclear submarines.Nice, but stupid. And dangerous. Here's why:
It's lovely having ships that are vastly more capable than those of the past. And there's no doubt that a modern aircraft carrier can dominate the skies over a nice, hefty chunk of territory. And there's also equally no doubt that a modern missile sub can pretty much destroy half a continent. But power isn't the only criterion you're interested in. There are three other important factors.
First, Obama seems to think that ships don't get destroyed in wartime. An aircraft carrier is the biggest, fattest target ever to float, and a lot of creativity has gone into figuring out how to destroy it. That's why aircraft carriers sail in the middle of giant task forces, whose sole purpose is to protect the carrier. But the odds of losing a carrier in a full-up war are non-trivial. For that reason, you need redundancy, both in task force ships and in task forces themselves.
Second, highly capable ships are extremely expensive. Sometimes it's better to build cheaper, less capable ships, which can be moved around more flexibly.
Third, the most likely naval foe of the next 50 years is China. If they confront us, they're likely to do it everywhere, all at once. That means that we could face pressure from East Africa all the way to the US west coast. A carrier task force can control a chunk of sky and ocean maybe 750 miles in radius, but it sure can't control half the world simultaneously. Moving carriers around is slow and dangerous. You need enough task forces to meet the plausible threats.
It's simple to draw down the size of your navy by dropping out a carrier task force or two. But doing so allows your most likely enemy to put you in a serious hole with a couple of lucky hits, and then overwhelm your capabilities by causing trouble in a lot of places at once.
Obama seems to think that the navy is there to be impressive. He doesn't quite understand that it's only impressive if your adversaries think that it can fight a real war.